Chemistry 1 (Objective) & Chemistry 2 (Essay)

Chemistry 1 (Objective) & Chemistry 2 (Essay) – WAEC 2025 Complete Guide

Introduction

Understanding WAEC Chemistry Papers

Chemistry is a core science subject in the WAEC examination. It plays a critical role in science-related courses like medicine, pharmacy, engineering, and biochemistry. To evaluate students' grasp of this subject, WAEC divides Chemistry into three papers:

Paper 1 – Objective (Multiple Choice)
Paper 2 – Essay (Theory and Calculations)
Paper 3 – Practical (covered in a separate article)

This article focuses on Paper 1 and Paper 2, guiding you on what to expect and how to prepare effectively.

The Importance of Paper 1 and Paper 2 in Chemistry

Chemistry Paper 1 tests your speed and precision across a wide range of topics using 50 multiple-choice questions. Paper 2, on the other hand, evaluates your deep understanding, problem-solving skills, and ability to explain, draw, and calculate in essay form.

To pass Chemistry, and even aim for distinctions, you need to perform well in both papers. Scoring high in Paper 1 provides a strong foundation, while Paper 2 allows you to show in-depth knowledge and earn more marks through structured answers.

WAEC 2025 Chemistry Paper Structure

Paper 1 – Objective Overview

This section includes 50 multiple-choice questions from all areas of the syllabus. You must answer all within 1 hour.

Marks: 50 marks
Question Style: Direct questions with four options (A–D)
Topics Covered:
- Atomic structure
- Periodic table
- Organic and inorganic chemistry
- Calculations
- Chemical bonding
- Electrolysis
- Acids, bases, and salts
- Gas laws

Paper 2 – Essay and Theory Format

This paper tests your comprehensive understanding and reasoning in Chemistry. It includes 2 sections:

Section A – Compulsory: Usually contains short-answer and calculation-based questions.
Section B – Choose any four questions out of five: These are essay-type questions with parts (a, b, c…).
Duration: 2 hours
Marks: 100 marks total

Marks Breakdown:

Section A: 25 marks
Section B: 4 questions x 20 marks = 80 marks
Neatness, correct units, and logical steps in calculations are essential.

Chemistry 1 (Objective): Key Topics and Question Style

Common Areas Covered in MCQs

To succeed in Paper 1, you should revise:

Atomic structure – protons, electrons, neutrons
Periodic table – groups, periods, trends
Chemical bonding – covalent, ionic, metallic
Acids and bases – pH, indicators, reactions
Gas laws – Boyle’s law, Charles’ law, ideal gas law
Chemical equations and mole concept
Organic chemistry basics – hydrocarbons, isomerism
Electrolysis – electrochemical cells, electrodes
Chemical kinetics and equilibria
Separation techniques – filtration, distillation

Sample Objective Questions with Answers

1. The number of neutrons in an atom of mass number 23 and atomic number 11 is:
A. 11
B. 12
C. 23
D. 34
Answer: B. 12
Explanation: Neutrons = Mass number – Atomic number = 23 – 11 = 12

2. Which of the following is a noble gas?
A. Nitrogen
B. Oxygen
C. Argon
D. Carbon dioxide
Answer: C. Argon
Explanation: Noble gases are in Group 18; Argon is one of them.

3. A covalent bond is formed by:
A. Transfer of electrons
B. Sharing of electrons
C. Loss of protons
D. Sharing of neutrons
Answer: B. Sharing of electrons

4. Which gas law relates pressure and volume?
A. Boyle’s Law
B. Charles’ Law
C. Dalton’s Law
D. Graham’s Law
Answer: A. Boyle’s Law

5. A solution with pH 2 is:
A. Strongly acidic
B. Weakly acidic
C. Neutral
D. Alkaline
Answer: A. Strongly acidic

Chemistry 2 (Essay): What to Expect

Types of Questions Asked

WAEC Chemistry Paper 2 includes:

Definition and explanation of concepts (e.g., types of bonds)
Balanced chemical equations
Problem-solving/calculations (e.g., titration, moles)
Drawing and labeling diagrams (e.g., electrolysis setup)
Comparison and trend explanation (e.g., atomic radius across periods)
Organic chemistry reaction mechanisms
Reasoning questions (e.g., why metals conduct electricity)

How to Structure Essay Answers

Begin with definitions if the question includes technical terms.
State formulas clearly when doing calculations.
Show full working – Marks are awarded for steps, not just the final answer.
Use correct units – Always include mol, dm³, g/mol, etc.
Use bullets for listing – Makes points clear.
Underlining keywords like “exothermic,” “oxidation,” “polymerization” adds clarity.

Pro tip: Label your diagrams and write neatly. Use subheadings if necessary for longer answers.

WAEC 2025 Likely Chemistry Essay Questions

Sample Questions and Answers

Question 1:
Define the mole and calculate the number of moles in 22 grams of CO₂ (Molar mass = 44 g/mol).

Answer:

Mole is the amount of substance that contains as many particles as there are atoms in 12 grams of carbon-12.
Moles = Mass / Molar mass = 22 / 44 = 0.5 moles

Question 2:
Describe the electrolysis of acidified water and write the half-cell equations.

Answer:

Electrolysis splits water into hydrogen and oxygen gases.
At cathode: $2H^+ + 2e^- → H_2(g)$
At anode: $2H_2O → O_2(g) + 4H^+ + 4e^-$
Oxygen is collected at the anode, and hydrogen at the cathode.

Question 3:
State three characteristics of transition elements.

Answer:

They form colored compounds.
They have variable oxidation states.
They act as catalysts in chemical reactions.

Chemistry Equations and Calculations

Balancing Equations

Balancing chemical equations is essential in WAEC Chemistry Paper 2. Questions usually require students to:

Identify reactants and products
Balance atoms on both sides of the equation
State physical states (solid, liquid, gas, aqueous)

Example:
Balance the equation:

\text{Na} + \text{H}_2\text{O} \rightarrow \text{NaOH} + \text{H}_2

Balanced Equation:

2\text{Na} + 2\text{H}_2\text{O} \rightarrow 2\text{NaOH} + \text{H}_2

Tips:

Start by balancing metals.
Then balance hydrogen and oxygen last.
Use coefficients (not subscripts) to balance.

Moles, Molarity, and Titration Calculations

These topics appear regularly in Section A of the essay paper. Mastery of formulas is key.

Formulas to Remember:

Moles (n) = Mass (g) / Molar Mass (g/mol)
Molarity (M) = Moles / Volume (dm³)
Titration Formula:

C_1V_1 = C_2V_2

(where C is concentration, V is volume)

Sample Question:
Calculate the number of moles in 250 cm³ of 0.2 M NaOH.

Solution:
Convert cm³ to dm³: 250 cm³ = 0.25 dm³
Moles = Molarity × Volume = 0.2 × 0.25 = 0.05 mol

Key Tip: Always convert volume to dm³ (1 dm³ = 1000 cm³).

Organic Chemistry in WAEC

Functional Groups and Reactions

You are expected to:

Identify functional groups (alcohols, carboxylic acids, alkanes, alkenes)
Recognize chemical reactions like substitution, addition, and esterification
Draw structural and molecular formulas

Examples of Functional Groups:

Group	Example	Functional Group
Alcohol	Ethanol	-OH
Alkene	Ethene	C=C
Carboxylic Acid	Ethanoic acid	-COOH
Ester	Ethyl ethanoate	-COO-

Common Reactions Tested:

Addition: Alkene + H₂ → Alkane
Esterification: Alcohol + Acid → Ester + Water

Question Example:
Write an equation for the reaction between ethanol and ethanoic acid.

Answer:

\text{CH}_3\text{COOH} + \text{C}_2\text{H}_5\text{OH} \rightarrow \text{CH}_3\text{COOC}_2\text{H}_5 + \text{H}_2\text{O}

Nomenclature and Isomerism

Students must know how to name organic compounds and recognize different isomers.

Example:
Draw two isomers of C₄H₁₀.

Butane (straight chain)
Methylpropane (branched)

Also, understand functional group isomerism (e.g., alcohol vs. ether) and chain isomerism (straight vs. branched chains).

Inorganic Chemistry Essentials

Periodic Table Trends

You will be asked to describe and explain:

Atomic radius trend across a period and down a group
Ionization energy trend
Electronegativity
Metallic and non-metallic character

Sample Essay Question:
Explain why atomic radius decreases across a period.

Answer:

Nuclear charge increases while shielding remains constant.
Electrons are pulled closer to the nucleus.
Hence, atomic size decreases.

Group Properties:

Group I: Alkali metals – reactive, soft, low melting points
Group VII: Halogens – form salts, diatomic, colored vapors

Transition Elements:

Form colored compounds
Exhibit variable oxidation states
Are good catalysts (e.g., Fe in Haber process)

Physical Chemistry Fundamentals

Gas Laws and Energetics

Be able to explain and apply:

Boyle’s Law: P ∝ 1/V
Charles’ Law: V ∝ T
Ideal Gas Law: PV = nRT

Sample Calculation:
A gas occupies 2 dm³ at 100 kPa. What is its volume at 200 kPa (temperature constant)?

Solution:
P₁V₁ = P₂V₂
(100)(2) = (200)(V₂)
V₂ = 0.5 dm³

Energetics:

Define exothermic and endothermic reactions
Draw energy profile diagrams
Calculate enthalpy change (ΔH)

Chemical Equilibrium and Kinetics

Equilibrium:

State Le Chatelier’s Principle
Predict effects of temperature, pressure, and concentration
Write equilibrium expressions

Kinetics:

Define activation energy and catalysts
Draw reaction rate graphs
Explain collision theory

Diagrams and Graphs in Chemistry Essay

Energy Profile Diagrams

You must draw and interpret diagrams for:

Exothermic and endothermic reactions
Activation energy
ΔH (enthalpy change)

Graphical Data Interpretation

You may be asked to:

Analyze temperature vs. reaction rate graphs
Interpret pH vs. time during titration
Read solubility curves

Ensure all graphs have:

Title
Labeled axes with units
Smooth curves or straight lines

Tips to Excel in WAEC Chemistry Papers

Time Management

Spend 1 minute per objective question in Paper 1
Allocate 25–30 minutes per essay in Paper 2
Use last 10 minutes to revise and correct units or formulas

Flashcards and Formula Sheets

Create flashcards for:

Functional groups
Gas laws
Periodic trends
Common equations and definitions

Stick a formula sheet to your wall or notebook for daily reference.

Past Question Practice and Mock Tests

Solve at least 3–5 past essay questions per week
Practice under exam conditions
Have your answers marked by teachers or senior students

Conclusion

WAEC Chemistry Papers 1 and 2 demand a balanced approach—speed and accuracy for Paper 1, and depth of understanding and clarity for Paper 2. Whether you’re calculating moles, drawing energy diagrams, or explaining periodic trends, a solid study routine and disciplined practice are the keys to success.

Focus on high-yield topics like mole concepts, equations, organic chemistry, and gas laws. Use flashcards, practice diagrams, and revise with past questions. Chemistry isn’t just about memory—it’s about logic, application, and smart learning.

FAQs

1. How many questions are in WAEC Chemistry Paper 1?
Paper 1 consists of 50 multiple-choice questions, and you must answer all within 1 hour.

2. Are calculations important in the essay paper?
Yes. Calculation questions on moles, titration, gas laws, and energetics are regularly tested in Section A and are usually compulsory.

3. How do I revise for Chemistry effectively?
Use flashcards, practice past questions, draw diagrams, and review formulas daily. Study in chunks and review weak topics more often.

4. What topics are frequently repeated in Chemistry WAEC?